Abstract: 【Objective】The objective of this study is to evaluate herbicidal activity of alkaloids from Cephalotaxus sinensis against four species of weeds and provide a basis for its further study. 【Method】 C. sinensis extract, total alkaloids, and eight alkaloids (drupacine, 11-hydroxycephalotaxine, cephalancetine A, isocephalotaxine, cephalotaxine β-N-oxide, 4-hydroxycephalotaxine, wilsonine and cephalotaxine) were measured by seed germination method and pot experiments, with Trifolium pretense, Amaranthus retroflexus, Lolium perenne and Sorghum sudanense as indicators.【Result】Seed germination experiment showed that C. sinensis extract, total alkaloids, drupacine, 11-hydroxycephalotaxine, cephalotaxine and cephalotaxine β-N-oxide had strong inhibiting effects on the growth of T. pretense with the EC₅₀ values of 634.35, 690.47, 69.47, 71.21, 174.11 and 243.12 mg·L^-1 against roots growth, and 411.79, 413.11, 68.52, 139.25, 237.72 and 413.62 mg·L^-1 against stems growth, respectively. C. sinensis extract, total alkaloids, drupacine, 11-hydroxycephalotaxine, cephalotaxine and cephalotaxine β-N-oxide showed strong inhibiting effects on the growth of A. retroflexus with the EC₅₀ values of 176.32, 29.69, 21.01, 48.08, 199.57 and 90.74 mg·L^-1 against roots growth, and 257.69, 46.20, 25.51, 47.85, 65.08 and 66.34 mg·L^-1 against stems growth, respectively. Only C. sinensis extract, total alkaloids and drupacine showed inhibiting effects on the growth of S. sudanense with the EC₅₀ values of 349.54, 254.27 and 84.71 mg·L^-1 against roots growth, and 556.50, 168.66 and 154.34 mg·L^-1 against stems growth, respectively. Only C. sinensis extract, cephalotaxine β-N-oxide and drupacine showed inhibiting effects on the growth of L. perenne with the EC₅₀ values of 214.40, 187.89 and 26.52 mg·L^-1 against roots growth, and 695.58, 290.15 and 122.26 mg·L^-1 against stems growth, respectively. The pot experiments showed that C. sinensis extract, total alkaloids, drupacine, 11-hydroxycephalotaxine and cephalotaxine had strong herbicidal effect in soil treatment against dicotyledon weeds T. pretense and A. retroflexus, and drupacine showed the strongest herbicidal effect with inhibitory rates of 78.89% and 81.11%, but low inhibitory rate of less than 25% against S. sudanense and L. perenne. Spraying treatment showed that the five samples had a weak herbicidal effect against dicotyledon weeds T. pretense and A. retroflexus with an inhibitory rate of less than 30%, and had no effect against S. sudanense and L. perenne.【Conclusion】C. sinensis alkaloids has potential herbicidal activities against dicotyledon weeds, and its main active constituent is drupacine, with an inhibiting effect on young buds growth.

Key words: Cephalotaxus sinensis, drupacine, cephalotaxine β-N-oxide, herbicidal activity, botanical pesticide